The present invention relates to an improved apparatus for executing a hemming process, which is capable of practically contracting cycle time in the execution of the hemming process.
In the course of manufacturing external plate bodies such as a hood, fenders, or side-doors, for assembling an automotive body, for example, a hem flange formed at an edge of an outer panel is folded backward to cause the folded-back hem flange to nip an edge of an inner panel so that both panels can eventually be combined with each other.
Conventionally, this method is called the "hemming process". Concretely, as shown in FIG. 5, a hem flange B is previously formed at an edge of an outer panel A by way of erecting it at a substantially right angle. Next, an edge of an inner panel C is superposed on the inner domain of the hem flange, and then a preliminary folding process is executed against the superposed hem flange by a predetermined folding angle by operating a preliminary-folding blade D. Finally, the superposed hem flange B is regularly folded by means of a regular folding blade E.
FIG. 6 is a lateral view of a conventional apparatus 1 for executing the hemming process, which executes the hemming process based on the method described below.
The reference numeral 3 shown in FIG. 6 designates a lower mold which is supported on a base 2. The reference numeral 4 designates an upper mold which is ascendably and descendably supported above the lower mold 3. The reference character A designates an outer panel which is previously furnished with a hem flange B and placed on the lower mold 3. The reference character C designates an inner panel which is loaded on the outer panel A.
The reference character D shown in FIG. 6 designates a preliminary folding blade which is disposed outside of the outer panel A via a pre-hemming structure 5. The reference character E designates a regular folding blade which is supported by the upper mold 4. The reference numerals 6 and 7 respectively designate a transmitting cam and a returning cam which are respectively held at specific positions above the pre-hemming structure 5 via a bracket 8 installed outside of the upper mold 4.
The pre-hemming structure 5 comprises a supporting frame 10 which is set to a position outside of the lower mold 3 mounted on the base 2 and a movable member 13 which is swingably supported by the supporting frame 10 via a pair of first and second links 11 and 12. The preliminary folding blade D is secured to the inner tip domain of the movable member 13.
The movable member 13 is externally drawn by the resilient force of a spring 14. Normally, the preliminary folding blade D is held in the state of being retracted to an upward position of the hem flange B of the outer panel A.
A roller 15 is rotatably supported by the first link 11 in order to swingably shift the movable member 13 in the direction of the hem flange B via own contact with the surface of the transmitting cam 6.
When the upper mold 4 descends in such a condition in which the outer panel A and the inner panel C are respectively set to the lower mold 3, initially, the surface of the transmitting cam 6 comes into contact with the roller 15 of the first link 11 of the pre-hemming structure 5 to cause the movable member 13 to shift itself in the preliminary folding direction (concretely, in the downward slant direction). As a result, the preliminary folding blade D at the tip of the movable member 13 comes into contact with the hem flange B to preliminarily fold the hem flange B by a predetermined folding angle.
When the upper mold 4 descends furthermore, the transmitting cam 6 leaves the roller 15 to cause the movable member 13 to be back to the initial position, thus causing the preliminary folding blade D to leave the hem flange as well.
Concretely, the returning cam 7 comes into contact with the roller 15 to bring the movable member 13 back to the initial position via functional effect of the returning cam 7. In consequence, the preliminary folding blade D is securely apart from the hem flange B.
When the upper mold 4 descends furthermore from the above-cited position, the regular folding blade E comes into contact with the hem flange B so that the hem flange B can fully be folded until closely being set to the inner panel C.
After completing the above-cited process for folding the hem flange B, the upper mold 4 is lifted so that it can be back to the initial position. Next, the outer and inner panels A and C complete with the hemming process are respectively drawn out of the lower mold 3 before eventually being delivered to the following process.
If it were aimed to contract cycle time in the hemming process and also contract cycle time in the operation of the whole production line equipped with a conventional hemming apparatus 1 based on the structure cited above, then, this conventional apparatus 1 still faces those technical problems to solve described below.
Concretely, when operating the pre-hemming structure 5 having the above structure to shift the preliminary folding blade D in the direction of the hem flange B, after completing a process for folding the hem flange B by lowering the upper mold 4, on the way of lifting the upper mold 4 back to the initial position, the transmitting cam 6 comes into contact with the roller 15 of the pre-hemming structure 5 to cause the movable member 13 of the pre-hemming structure 5 to again shift itself in the direction of the hem flange B. In other words, the movable member 13 ineffectively behaves itself.
Concretely, after completing the process to fold the hem flange B, if the upper mold 4 were lifted too fast, then, it will cause the pre-hemming structure 5 to perform a useless shifting operation. Therefore, any of these conventional hem-processing apparatuses cannot lift the upper mold 4 at a fast speed, and thus, there is a certain limit in terms of the capability to contract the operating cycle time.
In order to properly draw the outer and inner panels A and C complete with the hemming process from the lower mold 3, it is quite essential that enough space be secured between the lower and upper molds 3 and 4. However, since the transmitting cam 6 held by the bracket 8 substantially protrudes in the downward direction outer from the upper mold 4, in order to secure enough space between the lower and upper molds 3 and 4, it is quite essential for this conventional apparatus to extend the lifting stroke of the upper mold 4. This in turn obstructs the apparatus to contract cycle time in the execution of the hemming process.